Merge branch 'kubecost-cost-model' into 'master'

Documenting cluster cost management

See merge request gitlab-org/gitlab!43721

doc/.vale/gitlab/spelling-exceptions.txt

@@ -221,6 +221,7 @@ Kibana
 Kinesis
 Knative
 Kramdown
+Kubecost
 kubectl
 Kubernetes
 Kubesec

doc/user/clusters/cost_management.md

+---
+stage: Configure
+group: Configure
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
+# Cluster cost management
+
+Cluster cost management provides insights into cluster resource usage. GitLab provides an example
+[`kubecost-cost-model`](https://gitlab.com/gitlab-examples/kubecost-cost-model/)
+project that uses GitLab's Prometheus integration and
+[Kubecost's `cost-model`](https://github.com/kubecost/cost-model) to provide cluster cost
+insights within GitLab:
+
+![Example dashboard](img/kubecost_v13_5.png)
+
+## Configure cluster cost management
+
+To get started with cluster cost management, you need [Maintainer](../permissions.md)
+permissions in a project or group.
+
+1. Clone the [`kubecost-cost-model`](https://gitlab.com/gitlab-examples/kubecost-cost-model/)
+   example repository, which contains minor modifications to the upstream Kubecost
+   `cost-model` project:
+   - Configures your Prometheus endpoint to the GitLab-managed Prometheus. You may
+     need to change this value if you use a non-managed Prometheus.
+   - Adds the necessary annotations to the deployment manifest to be scraped by
+     GitLab-managed Prometheus.
+   - Changes the Google Pricing API access key to GitLab's access key.
+   - Contains definitions for a custom GitLab Metrics dashboard to show the cost insights.
+1. Connect GitLab with Prometheus, depending on your configuration:
+   - *If Prometheus is already configured,* navigate to **Settings > Integrations > Prometheus**
+     to provide the API endpoint of your Prometheus server.
+   - *For GitLab-managed Prometheus,* navigate to your cluster's **Details** page,
+     select the **Applications** tab, and install Prometheus. The integration is
+     auto-configured for you.
+1. Set up the Prometheus integration on the cloned example project.
+1. Add the Kubecost `cost-model` to your cluster:
+   - *For non-managed clusters*, deploy it with GitLab CI/CD.
+   - *To deploy it manually*, use the following commands:
+
+     ```shell
+     kubectl create namespace cost-model
+     kubectl apply -f kubernetes/ --namespace cost-model
+     ```
+
+To access the cost insights, navigate to **Operations > Metrics** and select
+the `default_costs.yml` dashboard. You can [customize](#customize-the-cost-dashboard)
+this dashboard.
+
+### Customize the cost dashboard
+
+You can customize the cost dashboard by editing the `.gitlab/dashboards/default_costs.yml`
+file or creating similar dashboard configuration files. To learn more, read about
+[customizing dashboards in our documentation](/ee/operations/metrics/dashboards/).